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| United States Patent |
6,044,951
|
|
Gutmann
, et al.
|
April 4, 2000
|
Claw toothing for a gearbox or the like
Abstract
In the case of a claw toothing for a gearbox or the like, of which the
claws are designed with an undercut and, viewed in cross-section with
respect to the longitudinal axis of the claws, have a flat or convex roof
profile, it is provided to improve the engagement that the plan view of
the claws tapers into a wedge shape towards the rotational axis of the
claw toothing and that the generatrices (5a, 5b) of the roof profile
and/or the sides, in the longitudinal direction of the claw, are straight
lines which go through the rotational axis (D).
| Inventors:
|
Gutmann; Peter (Munich, DE);
Tauschek; Georg (Munich, DE)
|
| Assignee:
|
BLW Praezisionsschmiede GmbH (Munich, DE)
|
| Appl. No.:
|
217013 |
| Filed:
|
December 21, 1998 |
Foreign Application Priority Data
| Jun 21, 1996[DE] | 196 24 772 |
| Current U.S. Class: |
192/108; 192/114T |
| Intern'l Class: |
F16D 011/14 |
| Field of Search: |
192/108,114 T
|
References Cited
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| 1597198 | Aug., 1926 | Howell.
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| 1866315 | Jul., 1932 | Merrill.
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| 2049127 | Jul., 1936 | Maybach | 192/108.
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| 2843927 | Jul., 1958 | Stock.
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| 3550738 | Dec., 1970 | Halibrand.
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| 3739664 | Jun., 1973 | Swanstrom, Jr.
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| 3780840 | Dec., 1973 | Thomas.
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| 5524738 | Jun., 1996 | Erlebach et al.
| |
| 5870923 | Feb., 1999 | Eisen et al.
| |
| Foreign Patent Documents |
| 0073985 | Mar., 1983 | EP.
| |
| 356109 | Feb., 1920 | DE.
| |
| 599714 | Jun., 1934 | DE.
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| 2052244 | May., 1971 | DE.
| |
| 28 55 712 | Apr., 1980 | DE.
| |
| 19514349 | Dec., 1995 | DE.
| |
| 59-73627 | Apr., 1984 | JP.
| |
| 347390 | Jun., 1960 | CH.
| |
| 26538 | ., 1913 | GB.
| |
| 1039905 | Jun., 1963 | GB.
| |
| 1542981 | Mar., 1979 | GB.
| |
| 2081822 | Feb., 1982 | GB.
| |
| 2106435 | Apr., 1983 | GB.
| |
Primary Examiner: Herrmann; Allan D.
Attorney, Agent or Firm: Helgott & Karas, P.C.
Parent Case Text
This Appln is a con't of PCT/EP97/03174 filed Jun. 18, 1997.
Claims
What is claimed is:
1. Claw toothing for rotation about an axis and including claws, for
example in a gearbox, each claw having an undercut and, in cross-section
with respect to a longitudinal axis of the claw, having one of a flat and
convex roof profile, in plan view each claw tapers into a wedge shape
towards the rotational axis of the claw toothing, a respective generatrix
of at least one of the roof profile and claw sides, in the longitudinal
direction of the claw, is a straight line extending through the rotational
axis.
2. Claw toothing according to claim 1, wherein the roof profile depicts one
of a triangular and polygonal gable.
3. Claw toothing according to claim 1, wherein the roof profile, viewed at
right angles to the longitudinal direction of the claw, is one of a half
ellipse and a rectangular shape.
4. Claw toothing according to claim 1, wherein a part of the claws of a
partner of the claw toothing is higher than the remaining claws.
5. Claw toothing according to claim 4, wherein each second claw is higher.
6. Claw toothing according to claim 4, wherein a height of the roof profile
corresponds at least partly to the extent of superelevation.
7. Claw toothing according to claim 1, wherein a surrounding height
section, forming a bottom edge of the roof profile, is flattening.
8. Claw toothing according to claim 3, wherein the roof profile includes
lateral rounding.
Description
BACKGROUND OF THE INVENTION
The invention relates to claw toothing for a gearbox or the like, of which
the claws are designed with an undercut and, viewed in cross-section with
respect to the longitudinal axis of the claws, have a flat or convex roof
profile.
Such claw toothings, in particular in gear-shift sleeves and gear wheels in
motor vehicle gear boxes, are subject to great wear. The roof profile of
the claws, which plays an important role for the first contact in the
meshing phase, is therefore to be designed in such a way that the
engagement occurs quickly and as much as possible without friction.
Moreover, the quality of the claw toothing is determined decisively by the
design of the sides; by the sides forming an undercut, a reliable
engagement is ensured.
From the U.S. Pat. No. 3,550,738 a synchronizing claw clutch coupling is
known in which individual claw elements protrude cam contour-shaped. In
this way, shifting gear at high speeds becomes possible, without causing
edge wear on the claws which occurs with conventional couplings. The known
claws have, according to FIGS. 4, 5; 8, 9 and 12, 13 respectively of this
U.S. Pat. No. 3,550,738, sides with slight undercuts as well as a flat or
convex roof profile, viewed cross-sectionally to the longitudinal axis of
the claw. The plan view shape of the claws in this case tapers into a
wedge shape towards the axis of rotation of the claw toothing and the
generatrices of the claw shape in the longitudinal direction of the claw
are straight lines which in the area of the sides run according to this
wedge shape.
In addition, a motor vehicle coupling which responds quickly and with low
friction is known (U.S. Pat. No. 5,524,738), the claws of which are
undercut on both sides; the claws, viewed in cross-section with respect to
the longitudinal axis of the claws, have a flat or convex roof profile.
Also here, the plan view of the claws tapers into a wedge shape towards
the rotational axis of the claw toothing and the generatrices of the claw
shape are at least in the area of the sides in the longitudinal direction
formed by straight lines which run according to the wedge shape. Hereby, a
shifting of gear at high speeds should be possible with little wear.
SUMMARY OF THE INVENTION
The object of the present invention is to improve such a claw toothing in
the sense that in achieving a claw shape simple to manufacture, the
contact upon engagement is particularly smooth and that the time of
engagement, decisive for the transfer of the torque, is achieved early
producing a large meshing surface in which case, by and large, the life of
the claw toothing should be improved.
With a claw toothing of the type mentioned at the start, this problem is
solved in that the plan view of the claws tapers into a wedge shape
towards the rotational axis of the claw toothing, that the generatrices of
the roof profile and/or the sides, in the longitudinal direction of the
claw, are straight lines which go through the rotational axis.
With this claw shape, called "spiral claw" in the following, the
generatrices form for the claw contour a spiral surface or a screw
surface, that is, the generatrices run in the form of radial straight
lines at various heights through the rotational axis and are twisted
towards one another, that is, unlike for the known claw shapes, the sides
in the case of the spiral claw do not describe a plane surface anymore,
but a spiral surface.
Preferably the spiral surface also extends into the area of the roof
profile so that, in accordance with the mutual rotation of the two
toothing partners in the area of the roof profile, the contact between two
claws is reduced to a line, that is, the engagement resistance is
particularly low. Similar conditions can be realized for other claw shapes
in that the roof profile at right angles to the longitudinal plane of the
respective claw is of convex design thus, for example, has a pitch
circular, or elliptic, or in a similar manner curved shape.
Such crowned roof profiles and correspondingly spiralled sides for claw
toothings can technically be realized by means of special hot and cold
calibration forming processes. They are particularly suited for gear boxes
in motor vehicles where, besides high durability, the ease of changing
gear is of significant importance.
For the operation of the claw toothing according to the invention, it is
not necessary that all claws have a particular, for example, plane or
convex roof profile. In general, it suffices to provide only part of the
claws with a particular roof profile; in this case, it is admittedly
necessary that the claws of this part are of a design to an extent higher
than the remaining claws. The height of the roof profile can in this case
correspond completely or partly to the extent of superelevation.
For example, it suffices if only each second claw in a partner of a claw
toothing is provided with a superelevated roof profile. The superelevated
claws ensure a reduced contact between the two partners of a claw toothing
at the moment of engagement and facilitates thus the changing of gears.
The more claws come simultaneously into contact with one another, that is,
the more claws have a roof profile improving the engagement, the longer
the life of the toothing, accepting admittedly an increasing engagement
resistance.
Only when all claws are provided with a particular roof profile is its
superelevation of no importance anymore; decisive then is only the design
of the claw shape and the roof profile in such a way that the contact
surface between the claws coming in contact with one another at the moment
of engagement is minimized and that the torsional tendency up to the
realization of the torque transferring edge engagement is optimal.
While, in the area of the roof profile, a line contact between the claws
coming in contact with one another upon engagement is strived for, only an
area contact is more suitably considered for the edge contact of the
claws.
The meshing performance is also further improved by designing, in a way
known in itself, a surrounding height section, forming the bottom edge of
the roof profile, as flattening, also known in the technical language as
"flat".
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
In the following, the invention is elucidated by means of the drawing.
Here,
FIG. 1 shows, in perspective representation, a section of a claw toothing
with three different claw shapes,
FIG. 2 shows, in half longitudinal section, a spiral claw with flat roof
profile and flat,
FIG. 3 shows a half section according to FIG. 2 through a spiral claw with
laterally sloped roof profile,
FIG. 4 shows a half section according to FIG. 2 through a spiral claw with
gable-shaped roof profile,
FIG. 5 shows a half section according to FIG. 2 through a spiral claw with
laterally rounded roof profile,
FIG. 6 shows a half section according to FIG. 2 through a spiral claw with
oval roof profile, and
FIG. 7 shows a complete spiral claw according to FIG. 6.
DESCRIPTION OF PREFERRED EMBODIMENTS
FIG. 1 shows a section from a toothing area of a claw toothing with three
different claw shapes, namely a claw 1 with a flat roof profile, a claw 2
with a laterally bevelled, flat roof profile and a claw 3 with a convexly
rounded roof profile. The three different claw shapes of a toothing body
are merely for the purpose of demonstration since different claw shapes in
the same toothing body do not seem useful, at any rate not when, as shown
here, the claws are of the same height. Admittedly, a combination would be
conceivable of flat claws 1, for example, with a height according to the
dotted line 4, and another claw shape, for example, according to the claw
2 with laterally bevelled roof profile or the claw 3 with rounded roof
profile in which case each of the roof profiles is superelevated with
respect to the flat claw 1. Suitably, such a claw body could alternately
have a flat claw without superelevation and a claw with superelevated roof
profile.
The different claw shapes according to FIG. 1 are shown relatively inexact,
that is, neither the undercutting of the sides can be seen nor is the
transition depicted between the actual basic body of the claw and its roof
profile.
FIG. 2 describes a so-called spiral claw 10 as half section in the
representation. Here, all generatrices of the sides 6a intersect the
imaginary axis of rotation D, that is, the generatrices 5a are formed by
straight lines which are twisted with respect to the axis of rotation D.
This means that the undercutting of the sides 6a, seen in the radial
direction to the axis of rotation D, decreases, that is, the angle of
undercutting .beta.1 at the front surface of the spiral claw 10 is greater
than the angle of undercutting .beta.2 at its rear surface. Viewed on the
whole, the side 6a represents a helicoidal surface, the generatrices of
which, conforming to the principle of a helicoidal surface, are straight
lines through the axis of rotation, of which the angle of twist, related
to a certain vertical step, is constant. Consequently, all edges of the
spiral claw 10 are defined by straight lines. A claw shape with claw body
10a, flat 10b and flat (rectangular) roof profile 10c were selected.
To elucidate the representation, the generatrices 5a are traced in each
case up to the rotational axis D so that one easily can see they run
conforming to the principle.
The following FIGS. 3 to 7 have in common that they show a spiral claw 10
each with the same basic body 10a, the same flat 10b, but different roof
profiles.
FIG. 3 shows a flat roof profile 10d with lateral bevel 11 that in
combination provides a polygonal profile.
FIG. 4 shows a gable-shaped roof profile 10e. The two roof slopes intersect
along the line 12 in the longitudinal median plane of the spiral claw 10
to produce a triangular profile. Again, only a half of the spiral claw 10
is shown; to simplify the representation, the other half is omitted.
Such half claw shapes are, of course, perfectly conceivable as valid claw
shape, for example, in gears which only are loaded in one direction of
rotation.
According to FIG. 5, the spiral claw 10 has again a flat roof profile 10f
which has a rounding 13 towards the side 6.
The spiral claw 10 has, according to FIG. 6, an oval roof profile 10g,
superimposed on a flat 10b, the latter superimposed on a basic body 10a,
which again is identical to the shape of the basic body according to FIGS.
2 to 6.
While FIG. 6 again only shows half a spiral claw, intersected in the
longitudinal median plane, the same claw is shown but completely according
to FIG. 7. Here, both the generatrices 5a of the side 6a and the
generatrices 5b of the undercut opposing side 6b are drawn. The convex
roof profile 10g is formed by half an oval which particularly can have the
shape of half of an ellipse.
With the aid of FIG. 7, which represents a completion, symmetrical to the
longitudinal median plane of the half claw according to FIG. 6, one can
imagine without any further that the representations in the FIGS. 2 to 5
are to be completed accordingly to a full claw shape. The dimensions of
the respective basic bodies with regard to their height h, their width b
and their radial length l are determined depending on the claw type and
claw shape desired on the finished gear.
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